An image display apparatus has heretofore been known which has one display surface and by which images corresponding to viewing directions can be observed. For example, Japanese Patent No. 3072866 has disclosed a stereoscopic display apparatus using matrix-like illumination, a lenticular, etc. as a technique for switching the directivity of illumination in a time sharing manner in displaying images in accordance with the viewing directions.
(A) and (B) of FIG. 19 are diagrams showing one example of the configuration of a conventional image display apparatus, wherein time sharing illumination is carried out by the combination of a light source group 100 composed of divided light sources L1, R1 to L3, R3 such as striped light sources and matrix-like light sources, and a lenticular 101 as a light diffusing element composed of lenses 1 to 3. In (A) of FIG. 19, among L1, R1 to L3, R3, the light sources of R1 to R3 are turned on, while the light sources of L1 to L3 are turned off. In (B) of FIG. 19, among L1, R1 to L3, R3, the light sources of L1 to L3 are turned on, while the light sources of R1 to R3 are turned off.
Owing to the lens function of the lenticular 101, the light sources R can only be observed when viewed from an observer located on the right side in the case of (A) of FIG. 19, while the light sources L can only be observed when viewed from an observer located on the left side. Thus, the light sources R and L are alternately turned on, and the display of a transmissive display element is switched between right-side display and left-side display accordingly, such that the observer on the right side can only observe right-side images, while the observer on the left side can only observe left-side images.
FIG. 20 is a diagram showing another example of the configuration of a conventional image display apparatus, which has been disclosed in, for example, Kaihatsu No. 0324, News Release (dated Sep. 30, 2003) by Mitsubishi Electric Corporation. This configuration is designed for stereoscopic display of a type called scan backlight, wherein a double-sided prism sheet 151 is disposed in the rear of a liquid crystal display element 150, and a light guiding plate 153 is disposed in the rear of the double-sided prism sheet 151. A first light source 152-1 and a second light source 152-2 are disposed at both ends of the light guiding plate 153. In the double-sided prism sheet 151, a front surface 151-1 has a lenticular structure, and a rear surface 151-2 has a prism structure. The light guiding plate 153 can change directivity by turning on/off the first light source 152-1 and the second light source 152-2. Owing to such a configuration, illumination light is caused to enter the right and left eyes of the observer in a time sharing manner, and images corresponding to the right and left eyes (a right eye image 154-1 and a left eye image 154-2) are displayed, thereby achieving the stereoscopic display. In FIG. 20, 155-1 denotes a first light source image, and 155-2 denotes a second light source image.